Crystalline para-oriented aromatic polyamide fiber, such as poly(p-phenylene terephthalamide) have been spun from concentrated sulfuric acid solution. While crystallinity is desired for many uses, there are applications where noncrystalline polymers and highly oriented fibers and films of amorphous oriented aromatic polyamides permit processing, modification or properties not attainable with crystalline products. Stable, highly amorphous character is not usually easy to achieve in condensation polymers and often the result is a high degree of solvent sensitivity and lack of dimensional stability at elevated temperatures.
Essentially amorphous aromatic polyterephthalamides are described in Macromolecules 1985, v. 18, pp 1058-1068 and J. Poly. Sci. Part A: Polymer Chem. V 25, 1249-1271 (1987). The noncoplanar conformation of certain of the polyamides disclosed in these publications is said to enhance solubility. The authors refer to solubility in amide solvents, such as tetramethylurea (TMU) even without LiCl, a known solubility promoter. Omission of the salt results in a cost-saving but more importantly, avoids the need for salt elimination by washing with water and drying. However, the particular soluble polyterephthalamide mentioned cannot be spun from sulfuric acid solution because the aromatic --CF.sub.3 group is unstable therein and is converted to --CO.sub.2 H and beyond. The present invention provides new aromatic homopolyterephthalamides and homo-2,6-naphthalamides that overcome such deficiencies and certain copolymers thereof, as well as fibers and films of the polymers.